I also have a jailbroken iPhone (4 to be exact) and I have no problems opening any apps. Safari opens in about 1 second, Chrome about 1 second, camera app in about 2 seconds. MyWi and other Cydia apps work flawlessly. Basically sounds like PICNIC is your problem.

Then again, I am not a "technology idiot" so making it "just work" was rather simple.